Jason, 56, was last seen leaving his home in Hackney on November 5 and police have issued new CCTV of him.
Officers are growing increasingly worried two weeks on as temperatures drop below zero at night.
Jason is 6 foot tall, of skinny build, and was last seen wearing black Sketchers, black bottoms and a black hoodie.
CCTV images show Jason in a shop on Theydon Road, Hackney, on October 22.
While this was filmed before he went missing, officers believe the footage better shows what Jason looks like now.
Sergeant Kevin Hook, from the Central East Command Unit, said: “We are increasingly concerned for Jason’s welfare, particularly now the weather has turned and temperatures drop to freezing at night.
“We are appealing to the public to let us know if they have seen him.
“Jason’s family are desperate to find him and concerned for his health. They are appealing for him to make contact – either with them or the police – to ensure he is safe and well.”
Anybody who sees Jason should call 101, quoting ref 876/07NOV.
